U.S. patent number 4,650,779 [Application Number 06/755,251] was granted by the patent office on 1987-03-17 for regeneration of pillared clays with gas containing a small amount of ammonia.
This patent grant is currently assigned to Mobil Oil Corporation. Invention is credited to Theodore P. Goldstein.
United States Patent |
4,650,779 |
Goldstein |
March 17, 1987 |
Regeneration of pillared clays with gas containing a small amount
of ammonia
Abstract
The useful life of a deactivated inorganic pillared clay
catalyst or an inorganic pillared clay sorbent saturated with a
steam-distillable organic sorbate is extended by adding a small
amount of ammonia to the regeneration gas or to the regeneration
steam.
Inventors: |
Goldstein; Theodore P.
(Yardley, PA) |
Assignee: |
Mobil Oil Corporation (New
York, NY)
|
Family
ID: |
25038340 |
Appl.
No.: |
06/755,251 |
Filed: |
July 15, 1985 |
Current U.S.
Class: |
502/38; 208/113;
208/310R; 502/54; 502/55 |
Current CPC
Class: |
B01J
29/90 (20130101) |
Current International
Class: |
B01J
29/90 (20060101); B01J 29/00 (20060101); B01J
021/20 (); B01J 038/08 (); B01J 038/12 (); B01J
038/06 () |
Field of
Search: |
;502/54,55,38,41,80,84,85,86 ;208/113,31R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Konopka; P. E.
Attorney, Agent or Firm: McKillop; A. J. Gilman; M. G.
Hobbes; L. P.
Claims
What is claimed is:
1. In the method for regenerating a deactivated inorganic acidic
pillared clay catalyst that contains coke residue acquired during
an acid catalyzed hydrocarbon reaction, said regeneration being
effected by contacting said deactivated catalyst with an oxygen
containing gas at elevated temperature under conditions effective
to remove said coke residues, the improvement whereby forming
regenerated catalyst with minimal loss of catalytic activity which
comprises including in said regeneration gas from about 0.001 to
5.0 volume percent of gaseous ammonia and heating said regenerated
catalyst in air or an inert gas under conditions effective to
desorb ammonia.
2. The method described in claim 1 wherein said hydrocarbon is a
gas oil and said reaction is catalytic cracking.
Description
FIELD OF THE INVENTION
This invention is concerned with pillared clays. It is particularly
concerned with inorganic pillared clays that have become
deactivated in use, either as sorbents for organic compounds, or as
catalysts in an organic conversion reaction. It is more
specifically concerned with an improved method for regenerating
such spent pillared clays.
BACKGROUND OF THE INVENTION AND PRIOR ART
The term "pillared clays" as used herein refers to pillared natural
and synthetic sheet-type (lamellar) silicates, and may properly be
regarded as pillared derivatives of such lamellar precursors. The
relationship of the structure and properties of the precursor
materials to the structure and properties of the pillared
derivatives are perhaps best shown by briefly considering the
natural smectite clays and their pillared derivatives.
The natural smectite clay minerals have a structure consisting of
superposed lamellas separated from each other by a layer of
hydrated cations. Each of the lamellas is a two-dimensional
polymeric oxyanion formed by two superficial layers consisting of
tetrahedral sites bonded to a central layer of octahedral sites.
The individual lamellas are about 9.6 A.U. thick. The 2:1 relation
between the tetrahedral and octahedral layers within a lamella is
characteristic of the smectite clays. Clays of the smectite type
include montmorillonite, beidelite, nontronite, and others. The
smectite clays have in common the property that they can undergo
ion exchange, for example with acids, i.e. the intercalated cations
are mobile. They also have the ability to intercalate metal
complexes, organic species, and solvent such as water with increase
in the interlayer distance. In some cases, such as with sodium
montmorillonite immersed in water, the osmotic swelling leads to
such large increase in the interlayer distance with concommitant
decrease of interlamellar bonding force as to delaminate the clay.
Such peptization is reversible.
It is evident from the foregoing description that the interlamellar
distance in the natural smectites is variable and depends to a very
large extent on the presence of liquid water. At 100.degree. C. to
200.degree. C., the interlamellar space decreases to about the
thickness of a monolayer of water. Thus, the precursor materials do
not have the well defined and fixed pore volume characteristic of
inorganic sorbents and porous catalysts. The concept of pillaring
smectite clays to create a porous network appears to have been
first described by Barrer and MacLeod in Trans. Farad. Soc. Vol.
51, p. 1290 (1955), when they used tetraalkylammonium ions to limit
the distance to which lamellas could be brought together. Since
that time other pillaring agents have been proposed, including
metal chelate complexes, and, most recently, polynuclear hydroxy
metal cations. The use of oligomeric metal cations such as hydroxy
aluminum and hydroxy zirconium cations can provide pillared phases
with interlayer free spacings in the range of 5 to 20 A, and which
are thermally stable above 500.degree. C. in the absence of water
vapor. Such materials are of interest as catalysts and catalyst
supports for processing petroleum streams, and as sorbents. For a
fuller description of pillared (and other modified) clay catalysts,
the reader is referred to a publication by T. J. Pinnavaia in
Science, Vol. 220, No. 4595, pp. 365-371 (Apr. 22, 1983), the
entire content of which is incorporated herein by reference for
background purposes.
The smectite clays are one example of a class of lamellar clays
that lends itself to pillaring. Other types of expandable
sheet-structure clay type minerals that also lend themselves to
pillaring include vermiculite, nontronite, saponite, hectorite,
biotite, magadiite, sauconite, bowlingite, and mixed-layer type
minerals such as illite-montmorillonite, rectorite, allevardite,
hydromicas, and others.
Pillared clays in general are recognizable because the basal plane
distance (interlamellar spacing) remains essentially unchanged on
progressive removal of water at elevated temperature. Basal plane
distance is readily measured by X-ray diffraction, as is known to
those skilled in the art. Furthermore, an outgassed pillared clay,
free of sorbate, has a significant sorption capacity for organic
compounds such as benzene. In general, a calcined clay
well-pillared with thermally stable inorganic polymer will have an
interlayer spacing of at least about 6 A.U. (Angstrom Units), and
may range up to about 20 A.U. It will have a nitrogen BET surface
area greater than about 100 m.sup.2 /g, and a nitrogen pore volume
of about 0.1 to about 0.6 cc/g. U.S. Pat. No. 4,176,090 to Vaughan
et al. and U.S. Pat. No. 4,238,364 to Shabtai describe such
pillared clays and their utilities. These are incorporated herein
by reference as if fully set forth.
As will be illustrated by example hereinbelow, clays pillared, for
example with oligomeric hydroxy aluminum and hydroxy zirconium
cations, have a serious deficiency. In the presence of steam at
elevated temperature the rigid three-dimensional structure at least
partially collapses with loss of pore volume. This limits the
potential usefulness of such structures to catalytic applications
in which no water is present, either in the feed or in the product,
and to applications which do not require periodic regeneration of
the catalyst by burning off coke deposits since such deposits
contain hydrogen and burning generates steam. It also limits the
use of such structures as sorbents to situations in which
desporption with regeneration of active sorbent is conducted in the
absence of steam.
It is an object of this invention to provide a method for extending
the useful life of pillared clay catalysts and sorbents. It is a
further object of this invention to provide a method whereby spent
pillared clay catalysts are regenerated without loss of catalytic
activity. It is a further object to provide a method for steam
regeneration of a pillared clay sorbent without loss of sorption
capacity.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE is a schematic representation of a pillared clay of the
smectite variety.
DETAILED DESCRIPTION OF THE INVENTION
The method of this invention is simple. A pillared clay catalyst
that has become deactivated in use concommitant with the
accumulation of carbonaceous residue (coke residue) on the catalyst
is regenerated by contact at elevated temperature with an
oxygen-containing gas, such as air, that contains about 0.001 to
0.5 volume percent added gaseous ammonia. This method of
regeneration very substantially reduces or eliminates the loss of
activity that accompanies regeneration in the absence of added
ammonia. While the reason for the effectiveness of the added
ammonia is not known, one may speculate that the steam formed on
burning the carbonaceous residue induces progressive collapse of
the pillars and that this results in loss of pore volume and
catalytic activity. By providing a non-acidic environment, the
added ammonia counteracts the effect of the steam.
The method of this invention is particularly applicable to
inorganic pillared clays that are deactivated in an acid-catalyzed
conversion reaction, and particularly to an acid catalyzed
hydrocarbon conversion since these reactions in general lead to
deposition of coke and the need for periodic regeneration. Periodic
regeneration is described in many patents, e.g. in U.S. Pat. No.
4,251,395 to Schwartz, which is incorporated herein by reference,
and generally consists of contacting the deactivated catalyst with
an oxygen containing gas at elevated temperature of about
1000.degree. F. As used herein, the term "acid catalyzed
hydrocarbon reaction " refers to a reaction known to be promoted by
so-called acid catalysts. Catalytic cracking, hydrocracking,
skelatal isomerization, catalytic dewaxing, and various aromatic
hydrocarbon reactions such as alkylation, dealkylation,
isomerization and disproportionation, are hydrocarbon conversion
reactions which fall in the category of acid catalyzed reactions.
Other reactions, such as alcohol dehydration, are also in this
class.
Known inorganic porous solids such as silica-alumina, acid-treated
clays, zeolites such as Zeolite X and Zeolite Y in the hydrogen
form or in the divalent or polyvalent metal form, and other
zeolites such as ZSM-5 are well known for their ability to catalyze
the foregoing hydrocarbon conversion reactions. Such catalysts are
known in the art as "acidic" catalysts. The term "acidic" as used
herein will be applied to pillared clays which either as formed or
as modified by ion-exchange with metal cations, exhibit catalytic
activity for an acid-catalyzed reaction. The term "inorganic" as
used herein means free of organic matter, i.e. an inorganic
pillared clay has pillars which are formed of inorganic oxides or
other inorganic species. Examples of pillared clays useful as
catalysts and sorbents, and their modifications for catalytic
purposes, are described in U.S. Pat. No. 4,176,090 incorporated by
reference hereinabove. Cracking catalyst based on pillared
smectites are described in U.S. Pat. No. 4,238,364 incorporated by
reference hereinabove.
As is known in the art, the acid catalytic activity of a zeolite or
other inorganic catalyst may be measured by its "alpha value",
which is the ratio of the rate constant of a test sample for
cracking normal hexane to the rate constant of a standard reference
catalyst. Thus, an alpha value=1 means that the test sample and the
reference standard have about the same activity. The alpha test is
described in U.S. Pat. No. 3,354,078 and in the Journal of
Catalysis, Vol. IV, pp 522-529 (August 1965), both of which are
incorporated herein by reference. Measurement of the "alpha value "
is useful to assess the extent of loss of catalyst activity
encountered on regeneration or on exposure to steam. However, other
conversions also may be used to assess catalytic activity.
It will be recognized by those skilled in the art that the catalyst
regenerated by the method of this invention will be at least
partially in the ammonium form. For purposes of this invention, it
is usually preferred to remove the adsorbed ammonia, e.g. by
calcining at about 538.degree. C. for about 1 hour. Such treatment
is usually regarded as effective to convert those catalytic sites
which are in the ammonium form to the hydrogen form.
A section through a typical inorganic pillared smectite is shown
schematically in the FIGURE. Shown therein are the negatively
charged lamellas cross-linked with inorganic (such as alumina)
pillars to form the fixed pore space. Metal or hydrogen cations
(not shown) are located in the pore space. More or less than four
lamellas may be present. Access to the pore space is probably
through the edges of crystal rather than by penetration of the
lamellas.
In another embodiment of this invention, a pillared clay sorbent
that has become saturated with a steam-distillable organic sorbate
that is free of aldehyde, ketone and carboxyllic acid substituents
may be regenerated with steam that contains a small amount of
ammonia to recover regenerated sorbent and separated sorbate. The
presence of about 0.001 to 5 volume percent of ammonia added to the
steam is very effective in lengthening the useful life of the
sorbent. This method is particularly applicable to the preparation
and recovery of natural and synthetic essential oils.
This invention will now be illustrated by examples which, however,
are not to be construed as limiting the scope thereof, said scope
being determined by this entire specification including the
appended claims.
EXAMPLES
Example 1
A pillared clay was prepared according to the method described in
U.S. Pat. No. 4,176,090 to Vaughan, et al., by treating a Volclay
bentonite with a polymeric solution of basic aluminum chloride and
sodium silicate at 150.degree. F. for about one hour. The pH of the
mixture was kept at 4.8 with periodic 3% NH.sub.4 OH additions.
Upon completion of the treatment, the product was filtered,
hot-water-washed and dried. Final calcination was at 1000.degree.
F. in air for two hours. The completion of the pillaring process
was indicated by the large surface area of the product which was
found to be 340 m.sup.2 /g, compared to 30 m.sup.2 /g for the base
material. Its cyclohexane adsorption was 6.7% indicating relatively
large pores. The chemical composition was found to be 55.2%
SiO.sub.2, 34.4 Al.sub.2 O.sub.3, 0.21% Na and traces of other
metals common to clay minerals.
Example 2
A portion of the pillared clay of Example 1 was treated at
538.degree. C. with saturated steam for 18 hours. At the end of
that time the catalytic activity for cracking normal hexane (alpha
value) was measured, as was the alpha value of the unsteamed
material. The unsteamed material was found to have an alpha value
of about 2.0, while the steamed material had an alpha value of only
1.4, showing loss of catalytic activity.
Example 3
Another sample of the pillared clay of Example 1 was steamed under
the same conditions as in Example 2 except that a small amount of
the steam was generated from aqueous ammonia. After 38 hours the
steamed catalyst was subjected to the usual precalcination at
538.degree. C. before measuring the alpha value, which in this
instance would cause desorption of adsorbed ammonia (i.e.
conversion of the pillared clay to the hydrogen form), followed by
contact with the normal hexane. Its alpha activity was found to be
1.9, i.e. about the same as the untreated pillared clay.
Example 4
A pellet of the pillared clay of Example 1 was used to sorb
nitrobenzene vapor. The pellet was placed in a test tube and steam
passed through the test tube. The condensate collected was a milky
suspension and the presence of nitrobenzene was evident from its
odor. Its presence was confirmed by its characteristic U.V.
absorption spectrum.
Example 5
Cineole (Eucalyptol) was sorbed in a sample of the pillared clay of
Example 1. Steam was then passed over the sorbent and the effluent
was condensed. The recovered cineole separated from the water layer
as a clear upper layer (its density being 0.92) and the
characteristic eucalyptol odor noted. Cineole has a boiling point
of 176.degree.-177.degree. C., but was readily recovered from the
clay sorbent by distillation with steam at a temperature about
100.degree. C.
* * * * *